printk: add Kconfig option to set default console loglevel

Add a configuration option to set the default console loglevel.  This
is, as before, still possible to override at runtime through bootargs
(loglevel=<x>), sysrq and /proc/printk.

There are cases where adding additional arguments on the commandline is
impractical, and changing the default for the kernel when being built
makes more sense.  Provide such a method here, for those who choose to
do so.

Also, while touching this code, clarify the difference between
MESSAGE_LOGLEVEL_DEFAULT and CONSOLE_LOGLEVEL_DEFAULT.

Link: http://lkml.kernel.org/r/1479676829-30031-1-git-send-email-olof@lixom.net
Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/printk.h b/include/linux/printk.h
index afe8cce..3472cc6 100644 (file)
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -50,10 +50,15 @@ static inline const char *printk_skip_headers(const char *buffer)
 #define CONSOLE_LOGLEVEL_SILENT  0 /* Mum's the word */
 #define CONSOLE_LOGLEVEL_MIN    1 /* Minimum loglevel we let people use */
 #define CONSOLE_LOGLEVEL_QUIET  4 /* Shhh ..., when booted with "quiet" */
-#define CONSOLE_LOGLEVEL_DEFAULT 7 /* anything MORE serious than KERN_DEBUG */
 #define CONSOLE_LOGLEVEL_DEBUG 10 /* issue debug messages */
 #define CONSOLE_LOGLEVEL_MOTORMOUTH 15 /* You can't shut this one up */
 
+/*
+ * Default used to be hard-coded at 7, we're now allowing it to be set from
+ * kernel config.
+ */
+#define CONSOLE_LOGLEVEL_DEFAULT CONFIG_CONSOLE_LOGLEVEL_DEFAULT
+
 extern int console_printk[];
 
 #define console_loglevel (console_printk[0])

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9bb7d82..65a619e 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -15,6 +15,21 @@ config PRINTK_TIME
          The behavior is also controlled by the kernel command line
          parameter printk.time=1. See Documentation/kernel-parameters.txt
 
+config CONSOLE_LOGLEVEL_DEFAULT
+       int "Default console loglevel (1-15)"
+       range 1 15
+       default "7"
+       help
+         Default loglevel to determine what will be printed on the console.
+
+         Setting a default here is equivalent to passing in loglevel=<x> in
+         the kernel bootargs. loglevel=<x> continues to override whatever
+         value is specified here as well.
+
+         Note: This does not affect the log level of un-prefixed prink()
+         usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
+         option.
+
 config MESSAGE_LOGLEVEL_DEFAULT
        int "Default message log level (1-7)"
        range 1 7
@@ -26,6 +41,10 @@ config MESSAGE_LOGLEVEL_DEFAULT
          that are auditing their logs closely may want to set it to a lower
          priority.
 
+         Note: This does not affect what message level gets printed on the console
+         by default. To change that, use loglevel=<x> in the kernel bootargs,
+         or pick a different CONSOLE_LOGLEVEL_DEFAULT configuration value.
+
 config BOOT_PRINTK_DELAY
        bool "Delay each boot printk message by N milliseconds"
        depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY